1. Field of the Invention
The present invention generally relates to optical inspection systems and, more specifically, to systems for the in-line analysis of electronic circuits. The present invention more specifically relates to systems equipped with digital cameras.
2. Discussion of Prior Art
FIG. 1 schematically shows an installation of the type to which the present invention applies as an example. Electronic circuits IC, for example supported by a printed circuit board ICC, are placed, for example, on a conveyor of an in-line optical inspection installation. Such an installation comprises a system 2 of digital cameras, connected to an image processing computer system 3. Conveyor 1 is capable of moving in a plane X, Y (generally horizontal) and, for a series of photographs, in one of the two directions only, that is, direction X.
To decrease processing costs, it is generally desired to compensate for a limited quality of the images by a digital processing of these images. In particular, it has already been provided to compensate for a low camera resolution by taking several images, slightly offset with respect to one another in both directions of the plane and by implementing a so-called super-resolution technique.
For example, document WO2009/090633 describes an inspection installation using an array network of several digital cameras which is displaced with respect to the photographed object to implement a super-resolution technique. To increase the image resolution in both directions of the plane by means of such a system, a camera network must be used and displaced, either in both directions of the plane, or in an oblique direction with respect to the conveying direction. This complicates the system mechanism and increases its cost due to the accuracy required for the drive motors.
Another object of some optical inspection systems is to obtain three-dimensional images. An installation such as described in the above-mentioned document is not adapted to the reconstruction of three-dimensional images.
It would be desirable to have an installation for analyzing objects of integrated circuit type by image processing, which allows the use of a lesser number of cameras than conventional system, with no loss of resolution.
It would also be desirable to have an installation adapted to three-dimensional analysis.
It would also be desirable to have a system of low cost as compared with known solutions.